Gradle: Self-extract required contents from Uber Jar (#1015)

Closes #1007

build.gradle

@@ -25,6 +25,22 @@ jar {
 
 shadowJar {
   mergeServiceFiles()
+
+  from ('conf') {
+    into 'conf'
+  }
+
+  from ('html') {
+    into 'html'
+  }
+
+  from ('installation') {
+    into 'installation'
+  }
+
+  from ('ssi') {
+    into 'ssi'
+  }
 }
 
 repositories {

src/org/loklak/LoklakServer.java

@@ -24,16 +24,20 @@
 import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.security.KeyStore;
 import java.security.PrivateKey;
 import java.security.Security;
 import java.security.cert.Certificate;
 import java.security.cert.X509Certificate;
+import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Properties;
 import java.util.Random;
 import java.util.Set;
+import java.util.jar.JarEntry;
+import java.util.jar.JarFile;
 import java.util.regex.Pattern;
 
 import javax.servlet.MultipartConfigElement;
@@ -136,7 +140,9 @@
 
 
 public class LoklakServer {
-
+
+    private final static String[] FOLDER_TO_EXTRACT = { "conf", "html", "installation", "ssi"};
+
     public final static Set<String> blacklistedHosts = new ConcurrentHashSet<>();
 
     private static Server server = null;
@@ -193,6 +199,9 @@ public static String getServerURI() {
 
     public static void main(String[] args) throws Exception {
     	System.setProperty("java.awt.headless", "true"); // no awt used here so we can switch off that stuff
+
+        // extract contents
+        extractContents();
 
         // init config, log and elasticsearch
         Path data = FileSystems.getDefault().getPath("data");
@@ -341,6 +350,47 @@ public void run() {
         // The main termination line is therefore inside the shutdown hook.
     }
 
+    private static void extractContents() {
+        // Check if we're running inside a JAR file
+        if(!LoklakServer.class.getResource("LoklakServer.class").getPath().startsWith("file:"))
+            return;
+
+        try {
+            JarFile jar =
+                    new JarFile(LoklakServer.class.getProtectionDomain().getCodeSource().getLocation().getPath());
+            Enumeration entries = jar.entries();
+            while (entries.hasMoreElements()) {
+                JarEntry file = (JarEntry) entries.nextElement();
+
+                for (String s : FOLDER_TO_EXTRACT) {
+                    if (file.getName().startsWith(s + File.separator)) {
+                        extract(jar, file);
+                        continue;
+                    }
+                }
+            }
+        } catch (IOException e) {
+            Log.getLog().warn("An exception has occurred while extracting contents from JAR File", e);
+            Log.getLog().info("Exiting due to fatal error ...");
+            System.exit(1);
+        }
+    }
+
+    private static void extract(JarFile jar, JarEntry file) throws IOException {
+        Path workingDirectory = Paths.get("").toAbsolutePath();
+        File target = new File(workingDirectory.toString() + File.separator + file.getName());
+
+        if (target.exists())
+            return;
+
+        if (file.isDirectory()) {
+            target.mkdir();
+            return;
+        }
+
+        Files.copy(jar.getInputStream(file), target.toPath());
+    }
+
     // initialize harvester
     private static void initializeHarvester() {
         String type = DAO.getConfig("harvester.type", "classic");